where \(\theta _1,\theta _3\in \mathbb {R}^{d\times d}\) , and \(\theta _2,\theta _4\in \mathbb {R}^{d}\) , and \(\sigma \)  is a component-wise regularized ReLU activation function.
The form of the assumption controls the growth of its derivatives, and is used widely [1]}, [2]}.
